Method of determining relative times of development of photographic plates and films for different temperatures.



A. WATKINS. METHOD OF DETERMINING RELATIVE TIMES OF DEVELOPMENT OF PHOTOGRAPHIG PLATES AND FILMS FOR DIFFERENT TEMPERATURES. APPLICATION TILED NOV.29,1909

1,004,947, Patented Oct. 3, 1911.

[UNITED STATES PATENT OFFICE.

ALFRED WATKINS, OF THE IMPEEIAL MIILLS, HEREFORD, ENGLAND.

METHOD OF DETERMINING RELATIVE TIMES OF DEVELOPMENT OF PHOTOGRAPHIC PLATES AND FILMS FOR DIFFERENT TEMPERATURES.

Specification of Letters Patent.

Patented Oct. 3,1911.

Application filed November 29, 1909. Serial No. 530,299.

' subject of the King of Great Britain, residing at The Imperial Mills, Hereford, in the county of Hereford, England, photographicapparatus manufacturer, have invented a certain new and useful. Method of Determining Relative Times of Developmcntof lhotographic Plates and Films for Different 'lemperatures, of which the following is a specification.

in the specification of my United htates Patent No. 933605 I have described apparatus for determining the relative times of development of "zotographic plates or films for different ,tempemtures comprising two relatively movable slides, one bearing a temperature scale and the other a logarithmic scale, which scales are adjustable with respect to eachother, and I have mentioned that a thermometer can be supplied. as part of the appa'atus, the scale of the thcrlnxuneter itself in that case being used as atemperatln'e scale. Since completing the said application I have discovered that it is not essential that the thern'unncter should bear a scalc,an l the present inveir tion relates to a method of directly indicating the relative times of development of any photographic plates or films for different lBIHPGl'utllll-BS by means of tl'ie-expal'isiou of a tluid by modifying the apparatus de scribed in. the said specification in either of two Ways. in the first form the thormonr etcr hears a single mark thereon, which mark denotes a. degree of temperature corresponding with which the proper time of development of a particular developer has been ascertained by experience, and the division on the relatively movable logarithmic scale denoting the said proper time of development is brought into register with the mark.

The invention Will be explained With-referencc to the accompanying drawings, in which-- Figure 1 is a perspective view of one form of apparatus for determining the relative times of development accord ng to the invention. Fig. :2 is a taco view of a modified term of apparatus.

In Fig. l of the drawings 2? is a thermometric tube containing lluid (Z', and with ,the exception of the marl: (Z is ungraduated; the marl; (Z for instance, and by Way of example, isassumed' to be placed on the tube 6 in a positlon indicating atempera- 'ture of 6 is an outer tube inclosing the inner tube d, f is a logarithmic scale of ipaper or 'oth'er suitable material that bears ja proper relation to the ordinary thermometric scale that would be suitable for the 't-hermmnetrie tube (Z. The marl: (Z being assumed at the logarithmic scale is set relativel; to the tube (Z so that the division on the scale denoting the predetermined time of development correspond ing' with. the (30 temperature is in register with the mark (Z In Fig. 1 this requisite time is assumed for example to be 6% minutes. Should the temperature increase so that the fluid rZ rises to a height COL'LGSPOIKling with a temperature of the reading on the logarithmic scale opposite the height of the fluid would, as shown in Fig. 1, then be minutes for the same class of do VOlOPGI. and plate.

The logarithmic scale is made adjustable bv making it as on endless'bzmd a passing over rollers Z) mounted in a skeleton frame I) and suspended in the tube (2, the thermometer being" in'ovidcd with a cap 0 which can lie reiuoved to operate this band by the lingers so that for other classes of plate, the setting of the scale can be adjusted and the read ings. va rice. accordingly.

The second form of construction illustrated in Fig. 2 of: the drawing relates to an application of the same principle for use with the logarithmic scale fixed in relation. to the thermometer and not movable. To this case a certain time of development cor root for a plate and a fixed dilutionol it stated developer is fixed relation to the height of the fluid at a antlm'd temperature. As the temperature increases of dccreases, the fluid in the tube rises or descends, and the operator then reads oil the time of development opposite the height of the fluid c in the tube (Z' and uses that particular time. For example, as shown in the drawing, assume that the thcrm-tmetcr is so constructed that at a temporal-NFC of {$0 the height of the mercury in the tube (Z Wlll be opposite 3-1; minutes development on the fixed logarithn'lic scale for ajtnediuin plate and that the temperature rises to the time on the logarithmic scale will he 8} minutes for the same class of plate and developer. This time of development will also he correct for other makes of plate with the same developer, provided. that'the dilution or concentration of the developer he so modified for the particular plate that the same development result is obtained in minntc-n at 60 was attained with the plate and the developer for which the thermometer was that constructed, and these dilutions or concentrations (it the developer :ter sperifie types of plates can he i mlieated in the imtrnetioras issued with the instrument and he printed on the hack ot the lflgai'itllllll mule or any other part of the the. non'ietel'.

inn :1 a 'ale (remix-noted entirely from (Xpmimental data, it may he found to depart somewhat front the logarithn'iie form, but it Could still. he used as part of this. in- YOIIilOtl w ith sntlit'iently accurate resnlts. v

logarithmie SCtllG used in the ahm'e in: two (:enstrm-tions is preparetil or calculated event-ding; to the instrnntions (ordained in the speeitiea'tion to my United States Patent Having thus described the nature of my said invention and the heat means I know of earrying the seine into practical effect, I claim:

1i Almaratns for direetly indicating the length of time for the development of photographic plates or films by the expansion of a fluid, comprising a tube, fluid contained in the tube, the tube hearing a mark corresponding with the height of the fluid in the tube at a selected temperature, and a logaritlnnie scale having dii'isi'ons representing periods of development, 011601 said (llVlsions heing adapted to be in register with the Stllt'l mark, so that the height of the thud at any tempm'atin'e registers with the division on the scale representing the period of time for the development at that tmnperatare, snlmlantiall x as described.

Apparatm for direrlly il'nlicating the length of time ror the development of photographic plates or films by the expansion of a fluid, comprising an. enter tnhe, an inner tithe inelesed in the enter tnhe, fluid contained in the inner lnhe, the said inner tube hearing a mark ((11'3't. i;l)(llllg withlhe height of the finial in the tulle at a selected tcinperatln'e, a logaritlnnit' male morahly mounted within the Ftlltl tube. having di\isions representing pcl'imlH ot' :lerelopn'lent and adapted to he moved to hring an (livi- .-:ion thereon in register with. the mark as and for the purpose described so that the height of thefinid in the tube at a selected ters with the division on the scale representing the period of time for 1110 development at that temperature, substantially as de scribed.

l'n testimony whereof I have signed my name to this specification in the presence of two snhserilinng witnesnes.

A L FRED NA Kl NS.

ll itnesses:

Jonnvn Truman, O, L. lhmmrnr. 

